This road sign is in Oregon. The picture of this road was taken from an Amtrak train.

The road sign says...

+----------------+ | <- Barlow | | Needy 7 -> | | Monitor 13 -> | +----------------+the numbers are: 7 13 This is a PrimeRS because all the numbers are prime numbers. In addition, all of the prime numbers are reversible primes. All single digit prime numbers (2, 3, 5, and 7) are reversible primes. 13 is a reversible prime because reverse_digits(13) = 31 and 31 is prime. BARSfunc rsCardinalityEval: sqrt(7 - mult_digits(13)) = 2 * There are two numbers in this road sign. * mult_digits(n) = product of the digits of n domain: n must be a prime number * 13 is prime; mult_digits(13) = 1*3 = 3 off-by-one BARSfunc rsCardinalityEval: 7 - sum_digits(13) = 2+1 * There are two numbers in this road sign. * sum_digits(n) = sum the digits of n domain: n must be a prime number * 13 is prime; sum_digits(13) = 1+3 = 4 off-by-one BARSfunc rsCardinalityEval: reverse_digits(13) % 7 = 2+1 * There are two numbers in this road sign. * reverse_digits(n) = the digits of n reversed domain: n must be a prime number * 13 is prime; reverse_digits(13) = 31

**Creator:** Gerald Thurman
[gthurman@gmail.com]

**Created:** 31 July 2012

This work is licensed under a Creative Commons Attribution 3.0 United States License.